Imagine a scenario where we have a chamber with air that is supersaturated with water vapour. In this ideal scenario there are no nucleation sites (e.g no suspended particles or nucleation on the walls of the chamber).

What is the physical/chemical mechanism that limits further supersaturation?

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    $\begingroup$ The wall of the chamber will serve as a nucleation site. If you magically make that impossible, then I guess you may get insanely high supersaturation, before molecular fluctuations in the air will become new nucleation sites. $\endgroup$ – Ivan Neretin Jun 17 '20 at 19:59
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    $\begingroup$ There is still ionization due cosmic rays and natural ( mostly radon ) radioactivity, which serves as nucleation centre source. It was used earlier as detector of energetic charged particles. $\endgroup$ – Poutnik Jun 17 '20 at 20:07
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    $\begingroup$ Okay, since it's a hypothetical scenario, we forbid also those. Basically the question then is if there exists a mechanism that enforces an upper limit or not (e.g. as pointed out by @Ivan Neretin molecular fluctuations)? $\endgroup$ – Treex Jun 17 '20 at 20:13
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    $\begingroup$ There are many such mechanisms; you turn one off, then another steps in. It is pretty much like death. $\endgroup$ – Ivan Neretin Jun 17 '20 at 20:15
  • $\begingroup$ @IvanNeretin - now, you just have to prevent the molecules from interacting with each other. Sounds easy to me... $\endgroup$ – Jon Custer Jun 17 '20 at 21:00